There has been known inkjet recording apparatuses to record a desired image on a recording medium by ejecting ink drops through nozzles of an inkjet printhead. Such inkjet recording apparatuses are used for various purposes, and various kinds of ink and recording mediums can be used in accordance with the purposes.
Examples of inkjet printheads include piezoelectric printheads which apply pressure to the ink in pressure chambers utilizing the displacement of piezoelectric elements to eject ink drops through nozzles communicating with the respective pressure chambers.
Among such piezoelectric printheads, there is a printhead that has densely-arranged nozzles to form a high-definition image. For example, there has been known a piezoelectric printhead-which has nozzles each communicating with a corresponding pressure chamber, with the sets of a nozzle and its corresponding pressure chamber arrayed two-dimensionally (see Patent Literature 1, for example).
FIG. 13A shows a circuit board 200 of an inkjet printhead viewed from above supposing that a head board 210 provided below the circuit board 200 can be seen through from above. FIG. 13B is a view of the lower surface, viewed from above, of the circuit board 200 of the inkjet printhead supposing that the lower surface and the head board 210 can be seen through from above. Both of FIG. 13A and FIG. 13B are drawn supposing that pressure chambers 202 (described later) provided in the head board 210 below the circuit board 200 can be seen through from above.
FIG. 14 is a cross-sectional view of the circuit board 200 and head board 210 of the inkjet printhead.
As shown in FIG. 13A, the head board 210 of the inkjet printhead is provided with a plurality of nozzles 201. The pressure chambers 202, ink channels 203, and piezoelectric elements 204 (see FIG. 14) are provided corresponding to the respective nozzles 201. The circuit board 200 is provided above the piezoelectric elements 204, which circuit board 200 is provided with wires 205 to be connected to the respective piezoelectric elements 204. Each of the wires 205 is led to the upper surface of the circuit board 200 through a through hole via 206.
Each of the wires 205 is connected to a wire-connection member 207 provided outside of the area where the nozzles 201 and pressure chambers 202 are arrayed two-dimensionally. The wires 205 corresponding to the respective nozzles are each connected to the wire-connection member 207 avoiding the ink channels 203.
When the wire-connection member 207 is provided on both sides of the area where the nozzles 201 are arrayed two-dimensionally as shown in FIG. 13A and FIG. 13B, N/2 wires of each line have to run between adjacent ink channels (i.e., between A and B in FIG. 13A and FIG. 13B).
When the number of nozzles in one line is N, for example, the number of piezoelectric elements provided corresponding to the respective nozzles is also N. When the wires are led toward the right and left sides (upper and lower sides of each of FIG. 13A and FIG. 13B), the number of wires disposed between adjacent ink channels of the 1st nozzle row (i.e., between A and B in FIG. 13A and FIG. 13B) is N/2, where the density of wires is the highest on the left side. As the nozzle row moves on to the 2nd row, 3rd row . . . , the number of wires running between adjacent ink channels decreases one by one.
Dividing wires in half in such a way allows more space for wires compared to the case where all the wires corresponding the respective nozzles of each line are led toward the same direction. In order to achieve a printhead having densely-arranged nozzles, however, the printhead cannot provide enough space even if such a method is employed.